Effect of secondary infection with H9N2 avian influenza virus on tissue tropism and dissemination of Ornithobacterium rhinotracheale in SPF chickens

The purpose of this study was to investigate effect of secondary infection with avain influenza virus subtype H9N2 on tissue tropism and dissemination of ornithobacterium rhinotracheale (ORT) bacteria and H9N2 AI virus in different organs of specific pathogen free (SPF) chickens. Sixty, oneday- old SPF chicks ‘were randomly divided into three groups. They were kept in separate positive pressure isolators. On 21st day of study, the chicks in group 1 was inoculated intratracheally with 1×1010 CFU of ORT and three days later were adminstrated intraocularly with 1×106 EID50 of the H9N2, group 2 only inoculated with ORT bacteria. Group 3 as control was inoculated with PBS’ intraocularly. The samples from various tissues were collected at 6, 8, 10, 12, 14 and 16 days postinoculation (DPI). In group 1 chickens exhibited ruffled feathers, depression and reduced appetite, while in group 2 had minor clinical signs depression. The H9N2 AI virus was detected from lungs, trachea, bursa of fabricius, thymus, spleen and cecal tonsils of first group birds. The ORT was detected in the trachea, lung and liver of infected groups. The results showed that infected chickens with ORT under secondary infection by H9N2 AI virus cause exacerbate virulence and clinical signs and lesions
of ORT.